The feature has been in the works for almost a year now and will let users instantly translate written text without the need for an active internet connection.
The offline translation support in Google Lens is rolling out to users via a server-side update. Once you receive the update, you should see a new “Tap to download” prompt highlighting a new button next to most languages in the “Select Language” screen. Tapping on this button will download the respective language pack for offline translations.
Offline translation in Google Lens on Android is widely rolling out to users via a server-side update, but you will have to be on a recent version of the Google app in order to use the feature.